1. Field of the Invention
The present invention relates generally to a drill guide assembly and, more particularly, but not by way of limitation, to a drill guide assembly for use with medical devices and a method of manufacture thereof.
2. Description of the Related Art
Medical implants designed for use in orthopedics typically require a surgeon to drill holes into the bone in order to install the implant. Holes drilled into the bone freehand leave the potential for misalignment of the implant once installed into the bone. To prevent misalignment of the implant, a drill guide is frequently used to help guide the drill bit and ensure proper angulation and separation distance for each drill hole.
To reduce costs and simplify logistics in the operating room, medical device manufacturers prefer to use pre-sterilized and disposable drill guides. In making drill guides, materials such as plastic are preferred. Plastic drill guides can be injection molded in large quantities thereby reducing costs. However, drill guides made solely of plastic typically are not suitable for orthopedic surgery on the basis drill bits used in orthopedic surgery are normally made of metal. Metal drill bits spinning at high speed within a drill guide may create plastic shavings, which would drop into the patient during surgery. Making the drill guide solely from a material such as metal to prevent the creation of plastic shavings would be cost prohibitive. Therefore, medical device manufacturers frequently use metal guides inserted within a plastic body.
A metal guide inserted within a plastic body has several benefits. The metal guide prevents the drill bit from creating plastic shavings that drop into a patient during surgery while the plastic body allows for inexpensive mass production. The plastic body is typically manufactured using injection molding and the metal guides are then machined and attached to the plastic body by overmolding or press fit. In overmolding, molten plastic is poured around a metal guide during the injection molding process. An example of overmolded plastic drill guides with metal tubes is the BME Speed™ fixation system (BioMedical Enterprises, Inc, San Antonio, Tex.). The BME Speed™ fixation system has been on sale in the United States since 2011. In press fitting, the metal guides are inserted into the plastic body after the injection molding process. Both over molding and press fitting have disadvantages. In the overmolding process, it is more difficult to automate the injection molding process when a metal guide has to be positioned in the mold for each part. In press fitting, the tube receiving the metal guide must be a precise diameter. Creating a precise diameter of the tube ensures the metal guide remains firmly attached to plastic body while simultaneously preventing cracking of the plastic body. This however increases the manufacturing costs of the drill guide. Furthermore, drill guides that use press fits are also susceptible to rotation if the drill bit grasps the metal guide while spinning at high speeds.
Accordingly, a drill guide incorporating a metal guide or guides mated with a plastic body that is manufactured in such a way that overcomes the disadvantages of press fitting and overmolding would be beneficial.